1. Field
The disclosure relates to a bonding structure, and in particular relates to a bonding material and a bonding method for bonding a copper sheet to a heat dissipation substrate.
2. Description of the Related Art
Improving upon heat dissipation has reached a bottleneck for modulating a high heat generating device. Conventional FR4 substrates or aluminum-based metal substrates cannot conduct heat from a device to a heat dissipation device due to their low thermal conductivities. The described problem can be overcome by combining a copper sheet with an electrically insulative ceramic substrate to conduct the heat from a device to the heat dissipation device. The composite plate is the so-called direct bonded copper (DBC).
Although DBC may solve the heat dissipation problem, it is often processed at a temperature of over 1000° C. For forming a eutectic layer between the copper sheet and the ceramic substrate, the copper sheet should be firstly oxidized to form a copper oxide layer to bond with the ceramic substrate. Controlling uniformity and thickness of the copper oxide layer is difficult, thus, often, non-uniform heat dissipation results. If the copper layer needs to be patterned, an additional patterning process such as lithography and etching will be performed.
Accordingly, a novel method for bonding the copper sheet and the thermal dissipation substrate is called-for.